A: The role of antibody dependence enhancement: Virus infection begins with the adhesion to the cell surface, which is completed through the interaction between virus surface proteins and specific receptors and ligand molecules on target cells.

PDE is a partial differential equation.

PDE is an equation containing the partial derivative (or partial differential) of an unknown function. The highest order of the partial derivative of an unknown function in an equation is called the order of the equation. Second-order partial differential equations are widely used in mathematics, physics and engineering technology, and are traditionally called mathematical physical equations.